A typical load cell may be made from a single hollow column with sensors disposed upon its interior. This design concept is widely used for force measurement and works well except when the load cell may be subjected to externally applied pressures. Compensation for external pressure is problematic and complex in its implementation. This may lead to inaccuracies in the measurements made with such an arrangement. Strain gages may be applied to either the inside or the outside of the hollow column with equal success. An array of strain gages that measure both the axial component of strain and the Poisson effect 90 degrees to the axial component are typically used. Strain measurement gage pairs are usually placed equally spaced about the central axis of the hollow column.
The typical hollow column design suffers because, if the inner or outer portions of the column are subjected to pressure, the force measurement is affected by the pressure, as it is affected by axial force. Force and pressure measurements cannot readily be separated from each other. There are known systems that describe how to make this type of load cell by gage placement or electrical modification of a Wheatstone bridge insensitive to the pressure applied. However, with the known systems there may be limitations to the usage of their teachings due to the complexity of compensation techniques involved.
Sometimes hollow column load cells are also strain gaged to measure other physical forces being applied to the transducer. A good example of this is a multiplicity of strain gages placed 45 degrees to the axial axis of the transducer to measure torque being applied to the body of the transducer. This measurement is inherently insensitive to the pressure and axial force applied but the torque measurement can be improved by knowing the axial force and pressure applied and can be used to mathematically improve the accuracy of the torque measurement.